On Mon, Jul 21, 2014 at 05:15:51PM +0530, Amit Shah wrote:
> Instead of calling hwrng_register() in the probe routing, call it in the
> scan routine. This ensures that when hwrng_register() is successful,
> and it requests a few random bytes to seed the kernel's pool at init,
> we're ready to service that request.
>
> This will also enable us to remove the workaround added previously to
> check whether probe was completed, and only then ask for data from the
> host. The revert follows in the next commit.
>
> There's a slight behaviour change here on unsuccessful hwrng_register().
> Previously, when hwrng_unregister() failed, the probe() routine would
> fail, and the vqs would be torn down, and driver would be marked not
> initialized. Now, the vqs will remain initialized, driver would be
> marked initialized as well, but won't be available in the list of RNGs
> available to hwrng core. To fix the failures, the procedure remains the
> same, i.e. unload and re-load the module, and hope things succeed the
> next time around.
I'm not too comfortable with this. I'll try to take a closer look
tonight, but in the meantime...
> Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
> ---
> drivers/char/hw_random/virtio-rng.c | 25 +++++++++++++++----------
> 1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
> index a156284..d9927eb 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -35,6 +35,7 @@ struct virtrng_info {
> unsigned int data_avail;
> int index;
> bool busy;
> + bool hwrng_register_done;
> };
>
> static bool probe_done;
> @@ -136,15 +137,6 @@ static int probe_common(struct virtio_device *vdev)
> return err;
> }
>
> - err = hwrng_register(&vi->hwrng);
> - if (err) {
> - vdev->config->del_vqs(vdev);
> - vi->vq = NULL;
> - kfree(vi);
> - ida_simple_remove(&rng_index_ida, index);
> - return err;
> - }
> -
This needs to stay. register, and failure to do so, should occur in the
probe routine.
> probe_done = true;
> return 0;
> }
> @@ -152,9 +144,11 @@ static int probe_common(struct virtio_device *vdev)
> static void remove_common(struct virtio_device *vdev)
> {
> struct virtrng_info *vi = vdev->priv;
> +
> vdev->config->reset(vdev);
> vi->busy = false;
> - hwrng_unregister(&vi->hwrng);
> + if (vi->hwrng_register_done)
> + hwrng_unregister(&vi->hwrng);
> vdev->config->del_vqs(vdev);
> ida_simple_remove(&rng_index_ida, vi->index);
> kfree(vi);
> @@ -170,6 +164,16 @@ static void virtrng_remove(struct virtio_device *vdev)
> remove_common(vdev);
> }
>
> +static void virtrng_scan(struct virtio_device *vdev)
> +{
> + struct virtrng_info *vi = vdev->priv;
> + int err;
> +
> + err = hwrng_register(&vi->hwrng);
> + if (!err)
> + vi->hwrng_register_done = true;
Instead, perhaps we should just feed the entropy pool from here? We
would still need to prevent the core from doing so. Perhaps back to the
flag idea?
thx,
Jason.
> +}
> +
> #ifdef CONFIG_PM_SLEEP
> static int virtrng_freeze(struct virtio_device *vdev)
> {
> @@ -194,6 +198,7 @@ static struct virtio_driver virtio_rng_driver = {
> .id_table = id_table,
> .probe = virtrng_probe,
> .remove = virtrng_remove,
> + .scan = virtrng_scan,
> #ifdef CONFIG_PM_SLEEP
> .freeze = virtrng_freeze,
> .restore = virtrng_restore,
> --
> 1.9.3
>
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